Think Your Azure Architecture Is Private? If You’re Not Using a Private Link, You Might Be Leaking Data

 

I can’t tell you how many times I’ve heard this line in cloud architecture reviews.

Usually said by:

• Certified Azure Solutions Architects
• Cloud teams with Terraform scripts older than their CI/CD pipelines
• People are confident their traffic is “internal-only.”

Wait, aren’t service endpoints already private?

Yes, service endpoints sound secure. They let your Azure VNet talk to services like Storage or SQL “directly.”

But here’s the catch:

• The destination IP is still public.
• The service itself still lives in Azure’s shared infrastructure.
• It’s not a private IP — just prioritized traffic routing.

That means:

Auditors see traffic flowing to public IPs.

Data exfiltration protections won’t apply.

You might be technically non-compliant.

Azure Private Link

Here’s what Private Link does differently:

1. It maps Azure PaaS services (like Blob Storage or SQL) to a private IP in your VNet.
2. Traffic never leaves the Microsoft backbone.
3. There’s no exposure to the public internet at all. Even DNS resolution gets rerouted internally.

That means truly private access, the way you thought service endpoints were doing.

The Silent Risk You’re Probably Not Monitoring

Let’s play this out:

Scenario A: “Secure” Storage with Service Endpoints

• You restrict your subnet to use a service endpoint to storage
• You restrict the storage account to only accept traffic from that VNet
• You feel good

But:

• The storage endpoint is still a public IP.
• A misconfigured route table or DNS override could cause leakage.
• You have no easy way to inspect where the data goes.

Now, imagine an auditor shows up and asks, “Prove no data ever touched the public internet.”

Scenario B: Locked-Down Storage with Private Endpoint

• You create a private endpoint to storage.
• It gets a 10.x.x.x private IP in your subnet.
• You lock down DNS so myaccount.blob.core.windows.net resolves to that IP.
• You disable all public network access to the storage account.

Result?

Bulletproof isolation

Full compliance

No traffic leakage

Auditors smile (a rare event)

Why Architects Still Don’t Use It

Let’s call out the reasons:

1. It’s too complicated.
2. DNS configuration can be tricky, yes — especially with hybrid or custom setups.
3. It’s more expensive.
4. Slightly. But we’re talking cents, not dollars. And non-compliance fines? Way pricier.
5. It’s not in our Terraform module.
6. We haven’t updated our Infra-as-Code in 18 months.
7. We don’t need it. We trust Azure.
8. Look, Azure is amazing — but shared responsibility is real. Microsoft gives you the tools. It’s up to you to use them correctly.

How to Implement Private Link (Without Losing Your Mind)

Here’s a high-level roadmap:

1. Enable Private Endpoint

In your service (e.g., Azure SQL), go to Networking → Private Endpoint connections and add one.

2. Configure DNS

Use Azure Private DNS Zones or your custom DNS server to override:

myaccount.blob.core.windows.net → 10.x.x.x

Azure will auto-register this if you link to the private DNS zone.

3. Disable Public Network Access

Go to your resource and set Public Access → Disabled.

Now you’re truly private.

4. Test with nslookup and tracert.

Make sure you’re resolving and routing internally only.

The Checklist for Audits

If you’re in a regulated industry and not using Private Link, ask yourself:

• Is data leaving my VNet to a public IP?
• Can I prove that the data never touched public infrastructure?
• Am I using custom DNS that might break Private Link?
• Have I locked down public access to all Azure resources?
• Are my devs spinning up public-facing services via defaults?

If you answered “I’m not sure” to any of those, you’re at risk. Not just technically, but legally.

Cloud Security Is Not What You Intend — It’s What You Configure

Most Azure architects mean well. But good intentions don’t stop data leaks. Service endpoints might pass basic checks, but they won’t save you in a compliance audit. Private Link is the new gold standard. And in 2025, not using it isn’t “lean.”